This invention is directed to a magnetic recording and reproducing head and, in particular, to a magnetic recording and reproducing head in which information or data is recorded on a magnetic recording medium by means of a magnetic flux in a direction perpendicular to the plane of the recording medium defined by the direction in which the recording medium travels.
Perpendicular magnetization has recently been proposed in order to achieve high recording density on a magnetic recording medium such as magnetic tape or magnetic discs. In order to obtain high recording density on a magnetic recording medium, the interval of magnetic recorded patterns is required to be shortened. Herein, the interval is defined as the pitch of inverting of the magnetic moments. As the interval becomes shorter, the recorded magnetization of the medium tends to be oriented more perpendicular to the medium surface. Thus, a magnetic head for high density recording is desired to form a magnetic flux in a direction perpendicular to the medium surface.
In general, a perpendicular magnetic recording is a system which records and reproduces in the direction of thickness of the magnetic recording medium, that is, in the direction perpendicular to the medium surface. Such a system is introduced and explained in detail in "A Study on a Prospect of Magnetic Recording--Possibilities of Perpendicular Magnetic Recording" found in the Journal of Magnetics Society of Japan, Vol. 1, No. 2, pages 5-11 (May 26, 1977). Additional information relating to magnetic heads which record by means of perpendicular magnetization can be found in Japanese laid-open Patent Publication Nos. 53-32009, 54-51810 and 54-51804 by Shunichi Iwasaki. U.S. Pat. No. 4,210,946 of Iwasaki et al. discloses a type of magnetic recording medium which is suitable for use in a recording system which operates in a perpendicular magnetization mode. U.S. Pat. No. 4,251,842 to Iwasaki et al. discloses one type of a magnetic recording and reproducing device in which recording on the recording medium is performed in a direction perpendicular to the recording medium plane.
Although the above-identified publications describe magnetic heads which record in the perpendicular direction, they have not all been put into practical use due to the difficulties thereof. A ring-type magnetic head has heretofore been available for magnetic recording in the longitudinal recording direction. A ring-type head of thin film has been recognized as the most practical head and is currently in popular use. However, a system which uses the conventional ring-type magnetic head fundamentally using the longitudinal magnetization mode has disadvantages in that the effective magnetic field distribution cannot be attained in the high density recording region. As aforenoted, although described in the above-identified publications, magnetic heads for perpendicular magnetization recording have been difficult to be put into practical use. Such heads are insufficient to detect data recorded at high density and are poor in efficiency and reproduction. In addition, such heads have little tolerance for the shift of position between a magnetic head and the recording track on the recording medium which is inevitable in such devices.
In order to obtain high density magnetic recording, a magnetic head having high permeability magnetic thin film such as Permalloy as a magnetic pole has recently been proposed instead of the conventional magnetic head using sintered ferrite such as Ni-Zn as a magnetic core. Further, a magnetic recording medium consisting of an alloy magnetic thin film of Co-Cr or the like formed by sputtering, evaporating or plating on a substrate has recently been coming into practical use instead of the conventional medium on which needle like crystal powders such as Fe.sub.2 O.sub.3 are spread with a plastic binding material. The present invention is directed to magnetic recording and reproducing heads which record in the perpendicular mode. Based on the increasing use and acceptance of such heads, it is desired to provide an improved magnetic recording and reproducing head which records on a magnetic recording medium in a direction perpendicular to the plane of the recording medium.